Pile Cap Setup¶
The first tab. It defines the geometry, the number and arrangement of piles, the pile type, the materials and the cover.
Fields¶
Pile geometry¶
| Field | Unit | Note |
|---|---|---|
| No. of Piles in the Cap | — | From 1 to 30 |
| Specific Arrangement | — | Enabled depending on the number of piles |
| Pile Diameter | m | Enters \(A_p\), \(U\) and, in the Teixeira method, also \(N_p\) |
| Pile Type | — | Selects the construction coefficients of the three methods |
| Axis spacing | cm | Centre-to-centre distance between piles |
| Head Restraint | — | Pinned or Fixed |
Available arrangements¶
Up to eight piles, the program offers named arrangements — the layouts established in practice for each count. Above that, the distribution follows a rectangular pattern.
| No. | Arrangements |
|---|---|
| 1, 2 | Single |
| 3 | Triangle · Linear (X axis) · Linear (Y axis) |
| 4 | Square |
| 5 | Square + 1 centre · Pentagonal · Rectangular (2 and 3) |
| 6 | Rectangular (2×3) · Hexagonal |
| 8 | Rectangular (3-2-3) · Rectangular (4×2) · Rectangular (2×4) |
| 9 to 30 | Rectangular |
The Specific Arrangement field is only enabled when there is more than one option for that count.
Project limits¶
The ceiling of 200 piles in total is the one that matters in practice: a hundred caps of thirty piles each would be three thousand, and that is not what the program supports. The three limits act together, and whichever is reached first governs.
Pile cap and materials¶
| Field | Unit | Note |
|---|---|---|
| Cap Depth | m | |
| Head Level | m | Level of the pile head. Negative = cut off below ground |
| Edge Distance / Cover | cm | Distance from the cap face to the axis of the outer pile |
| Soil Height | m | |
| Exposure Class | — | CAA I to IV, defines the nominal cover |
| Unit Weight | kN/m³ | Of the concrete |
The head level changes the structural model
A head below zero means a pile cut off under the cap: the top node gets a soil spring, because there is ground around it.
A head at zero or above leaves the node free — the pile has an exposed length and behaves like a column fixed in the soil, with much larger displacements.
See Structural analysis.
Exposure class¶
| Class | Environment | Cover |
|---|---|---|
| CAA I | Mild | 3.0 cm |
| CAA II | Moderate | 3.0 cm |
| CAA III | Severe | 4.0 cm |
| CAA IV | Very severe | 5.0 cm |
The cover enters the calculation of the effective depth \(d\) and therefore the design for bending and shear.
Coordinates and loads per pile¶
The Pile Coordinates and Loads table is the heart of the tab. In it each pile receives:
- its position in the cap (X, Y);
- the loads applied at the head — axial force, shears and moments.
The sign follows the general convention: positive axial force is compression.
Raked piles¶
SPX allows an individual rake — each pile in the cap can have its own rake and azimuth. The feature opens a dedicated dialog.
| Parameter | Meaning |
|---|---|
| Rake | Angle from the vertical |
| Azimuth | Direction of the rake in the horizontal plane |
Check it in 3D
A swapped azimuth is the most common mistake, and it is invisible in the table. The 3D view of the pile cap shows the piles in their real position — two seconds of checking that prevent an entire project from being wrong.
Raked piles usually require enabling the vertical springs \(K_v\) in the structural analysis: without them, the raked pile is free to slide along its own axis.